Electronically latching micro-magnetic switches and method of operating same

ABSTRACT

A switch with an open state and a closed state suitably includes a cantilever having first and second states corresponding to the open and closed states of the switch, respectively. The switch may also include a magnet configured to provide an electromagnetic field that maintains said cantilever in one of the first and second states. Various embodiments may also include an electrode or electrical conductor configured to provide an electric potential or electromagnetic pulse, as appropriate, to switch the cantilever between the first and second states. Various embodiments may be formulated with micromachining technologies, and may be formed on a substrate.

This application is a continuation in part of application Ser. No.09/496,446, filed Feb. 2, 2000 which claims priority of ProvisionalApplication Serial No. 60/155,757 filed Sep. 23, 1999.

Partial funding for the development of this invention was provided byU.S. Government Grant Number Air Force SBIR F29601-99-C-0101,Subcontract No. ML99-01 with the United States Air Force; and the UnitedStates Government may own certain rights to this invention.

FIELD OF THE INVENTION

The present invention relates to electronic and optical switches. Morespecifically, the present invention relates to latching micro-magneticswitches with low power consumption and to methods of formulating andoperating micro-magnetic switches.

BACKGROUND OF THE INVENTION

Switches are typically electrically controlled two-state devices thatopen and close contacts to effect operation of devices in an electricalor optical circuit. Relays, for example, typically function as switchesthat activate or de-activate portions of electrical, optical or otherdevices. Relays are commonly used in many applications includingtelecommunications, radio frequency (RF) communications, portableelectronics, consumer and industrial electronics, aerospace, and othersystems. More recently, optical switches (also referred to as “opticalrelays” or simply “relays” herein) have been used to switch opticalsignals (such as those in optical communication systems) from one pathto another.

Although the earliest relays were mechanical or solid-state devices,recent developments in micro-electro-mechanical systems (MEMS)technologies and microelectronics manufacturing have mademicro-electrostatic and micro-magnetic relays possible. Suchmicro-magnetic relays typically include an electromagnet that energizesan armature to make or break an electrical contact. When the magnet isde-energized, a spring or other mechanical force typically restores thearmature to a quiescent position. Such relays typically exhibit a numberof marked disadvantages, however, in that they generally exhibit only asingle stable output (i.e. the quiescent state) and they are notlatching (i.e. they do not retain a constant output as power is removedfrom the relay). Moreover, the spring required by conventionalmicro-magnetic relays may degrade or break over time.

Another micro-magnetic relay is described in U.S. Pat. No. 5,847,631issued to Taylor et al. on Dec. 8, 1998, the entirety of which isincorporated herein by reference. The relay disclosed in this referenceincludes a permanent magnet and an electromagnet for generating amagnetic field that intermittently opposes the field generated by thepermanent magnet. Although this relay purports to be bi-stable, therelay requires consumption of power in the electromagnet to maintain atleast one of the output states. Moreover, the power required to generatethe opposing field would be significant, thus making the relay lessdesirable for use in space, portable electronics, and other applicationsthat demand low power consumption.

A bi-stable, latching switch that does not require power to hold thestates is therefore desired. Such a switch should also be reliable,simple in design, low-cost and easy to manufacture, and should be usefulin optical and/or electrical environments.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The above and other features and advantages of the present invention arehereinafter described in the following detailed description ofillustrative embodiments to be read in conjunction with the accompanyingdrawing figures, wherein like reference numerals are used to identifythe same or similar parts in the similar views, and:

FIGS. 1A and 1B are side and top views, respectively, of an exemplaryembodiment of a switch;

FIGS. 2A-H are side views showing an exemplary technique formanufacturing a switch;

FIGS. 3A and 3B are side and top views, respectively, of a secondexemplary embodiment of a switch;

FIG. 3C is a perspective view of an exemplary cantilever suitable foruse with the second exemplary embodiment of a switch;

FIG. 3D is a perspective of an exemplary embodiment of a switch thatincludes sectionalized magnetically sensitive members;

FIG. 3E is a side view of an exemplary cantilever that includes multiplemagnetically sensitive layers;

FIGS. 4A and 4B are exemplary side and top views of a third exemplaryembodiment of a latching relay;

FIGS. 4C and 4D are perspective views of exemplary cantilevers suitablefor use with the third exemplary embodiment of a latching relay;

FIG. 5 is a side view of a fourth exemplary embodiment of a latchingrelay;

FIGS. 6A and 6B are side and top views, respectively, of a fifthexemplary embodiment of a latching relay;

FIGS. 7A and 7B are side and top views, respectively, of an exemplary“Type I” mirror;

FIGS. 8A and 8B are side and top views, respectively, of an exemplary“Type II” mirror in a horizontal orientation;

FIGS. 8C and 8D are side and top views, respectively, of an exemplary“Type II” mirror in a vertical orientation;

FIG. 8E is a side view of an exemplary second embodiment of a reflectingmirror;

FIGS. 8F and 8G are top and side views, respectively, of an exemplarythird embodiment of a reflector/mirror;

FIGS. 9A and 9B are side and top views of an exemplary switch in a firststate;

FIGS. 10A and 10B are side and top views of an exemplary switch in asecond state; and

FIG. 11 is a top view of an exemplary 5×5 optical switch.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

It should be appreciated that the particular implementations shown anddescribed herein are examples of the invention and are not intended tootherwise limit the scope of the present invention in any way. Indeed,for the sake of brevity, conventional electronics, manufacturing, MEMStechnologies and other functional aspects of the systems (and componentsof the individual operating components of the systems) may not bedescribed in detail herein. Furthermore, for purposes of brevity, theinvention is frequently described herein as pertaining to amicro-electronically-machined relay for use in electrical or electronicsystems. It should be appreciated that many other manufacturingtechniques could be used to create the relays described herein, and thatthe techniques described herein could be used in mechanical relays,optical relays or any other switching device. Further, the techniqueswould be suitable for application in electrical systems, opticalsystems, consumer electronics, industrial electronics, wireless systems,space applications, or any other application. Moreover, it should beunderstood that the spatial descriptions (e.g. “above”, “below”, “up”,“down”, etc.) made herein are for purposes of illustration only, andthat practical latching relays may be spatially arranged in anyorientation or manner. Arrays of these relays can also be formed byconnecting them in appropriate ways and with appropriate devices.

A Latching Switch

FIGS. 1A and 1B show side and top views, respectively, of a latchingswitch. With reference to FIGS. 1A and 1B, an exemplary latching relay100 suitably includes a magnet 102, a substrate 104, an insulating layer106 housing a conductor 114, a contact 108 and a cantilever 112positioned above substrate by a staging layer 110.

Magnet 102 is any type of magnet such as a permanent magnet, anelectromagnet, or any other type of magnet capable of generating amagnetic field H_(o) 134, as described more fully below. In an exemplaryembodiment, magnet 102 is a Model 59-P09213T001 magnet available fromthe Dexter Magnetic Technologies corporation of Fremont, Calif.,although of course other types of magnets could be used. Magnetic field134 may be generated in any manner and with any magnitude, such as fromabout 1 Oersted to 10⁴ Oersted or more. In the exemplary embodimentshown in FIG. 1, magnetic field H_(o) 134 may be generated approximatelyparallel to the Z axis and with a magnitude on the order of about 370Oersted, although other embodiments will use varying orientations andmagnitudes for magnetic field 134. In various embodiments, a singlemagnet 102 may be used in conjunction with a number of relays 100sharing a common substrate 104.

Substrate 104 is formed of any type of substrate material such assilicon, gallium arsenide, glass, plastic, metal or any other substratematerial. In various embodiments, substrate 104 may be coated with aninsulating material (such as an oxide) and planarized or otherwise madeflat. In various embodiments, a number of latching relays 100 may sharea single substrate 104. Alternatively, other devices (such astransistors, diodes, or other electronic devices) could be formed uponsubstrate 104 along with one or more relays 100 using, for example,conventional integrated circuit manufacturing techniques. Alternatively,magnet 102 could be used as a substrate and the additional componentsdiscussed below could be formed directly on magnet 102. In suchembodiments, a separate substrate 104 may not be required.

Insulating layer 106 is formed of any material such as oxide or anotherinsulator such as a thin-film insulator. In an exemplary embodiment,insulating layer is formed of Probimide 7510 material. Insulating layer106 suitably houses conductor 114. Conductor 114 is shown in FIGS. 1Aand 1B to be a single conductor having two ends 126 and 128 arranged ina coil pattern. Alternate embodiments of conductor 114 use single ormultiple conducting segments arranged in any suitable pattern such as ameander pattern, a serpentine pattern, a random pattern, or any otherpattern. Conductor 114 is formed of any material capable of conductingelectricity such as gold silver, copper, aluminum, metal or the like. Asconductor 114 conducts electricity, a magnetic field is generated aroundconductor 114 as discussed more fully below.

Cantilever 112 is any armature, extension, outcropping or member that iscap able of being affected by magnetic force. In the embodiment shown inFIG. 1A, cantilever 112 suitably includes a magnetic layer 118 and aconducting layer 120. Magnetic layer 118 may be formulated of permalloy(such as NiFe alloy) or any other magnetically sensitive material.Conducting layer 120 may be formulated of gold, silver, copper,aluminum, metal or any other conducting material. In variousembodiments, cantilever 112 exhibits two states corresponding to whetherrelay 100 is “open” or “closed”, as described more fully below. In manyembodiments, relay 100 is said to be “closed” when a conducting layer120 connects staging layer 110 to contact 108. Conversely, the relay maybe said to be “open” when cantilever 112 is not in electrical contactwith contact 108. Because cantilever 112 may physically move in and outof contact with contact 108, various embodiments of cantilever 112 willbe made flexible so that cantilever 112 can bend as appropriate.Flexibility maybe created by varying the thickness of the cantilever (orits various component layers), by patterning or otherwise making holesor cuts in the cantilever, or by using increasingly flexible materials.Alternatively, cantilever 112 can be made into a “hinged” arrangementsuch as that described below in conjunction with FIG. 3. Although ofcourse the dimensions of cantilever 112 may vary dramatically fromimplementation to implementation, an exemplary cantilever 112 suitablefor use in a micro-magnetic relay 100 may be on the order of 10-1000microns in length, 1-40 microns in thickness, and 2-600 microns inwidth. For example, an exemplary cantilever in accordance with theembodiment shown in FIG. 1 may have dimensions of about 600 microns×10microns×50 microns, or 1000 microns×600 microns×25 microns, or any othersuitable dimensions.

Contact 108 and staging layer 110 are placed on insulating layer 106, asappropriate. In various embodiments, staging layer 110 supportscantilever 112 above insulating layer 106, creating a gap 116 that maybe vacuum or may become filled with air or another gas or liquid such asoil. Although the size of gap 116 varies widely with differentimplementations, an exemplary gap 116 may be on the order of 1-100microns, such as about 20 microns. Contact 108 may receive cantilever112 when relay 100 is in a closed state, as described below. Contact 108and staging layer 110 may be formed of any conducting material such asgold, gold alloy, silver, copper, aluminum, metal or the like. Invarious embodiments, contact 108 and staging layer 110 are formed ofsimilar conducting materials, and the relay is considered to be “closed”when cantilever 112 completes a circuit between staging layer 110 andcontact 108. Other embodiments use different formulations for contact108 and staging layer 110, such as those discussed below in conjunctionwith FIGS. 3 and 4. In certain embodiments wherein cantilever 112 doesnot conduct electricity, staffing layer 110 may be formulated ofnon-conducting material such as Probimide material, oxide, or any othermaterial. Additionally, alternate embodiments may not require staginglayer 110 if cantilever 112 is otherwise supported above insulatinglayer 106.

Principle of Operation

In a broad aspect of the invention, magnet 102 generates a magneticfield H_(o) 126 that induces a magnetization (m) in cantilever 112. Themagnetization suitably creates a torque on cantilever 112 that forcescantilever 112 toward contact 108 or away from contact 108, dependingupon the direction of the magnetization, thus placing relay 100 into anopen or closed state. The direction of magnetization in cantilever 112may be adjusted by a second magnetic field generated by conductor 114 asappropriate, and as described more fully below.

With continued reference to FIGS. 1A and 1B, magnetic field H_(o) 134may be applied by magnet 102 primarily in the direction parallel to theZ-axis such that the field is perpendicular to the primary dimension(e.g. the length) of cantilever 112. Magnetic field 134 suitably inducesa magnetization in cantilever 112, which may be made of soft magneticmaterial. Because of the geometry of cantilever 112, the magnetizationin cantilever 112 suitably aligns along the long axis of the cantilever,which is the length of cantilever 112 (parallel to the X-axis) in FIG.1.

The orientation of the magnetization in cantilever 112 is suitablydependent upon the angle (alpha) between the applied magnetic field 134and the long axis of cantilever 112. Specifically, when the angle(alpha) is less than 90 degrees, the magnetic moment (in) in cantilever112 points from end 130 of cantilever 112 toward end 132. Theinteraction between the magnetic moment and magnetic field H_(o) 134thus creates a torque in a counter-clockwise direction about end 130 ofcantilever 112 that moves end 132 upward, as appropriate, thus openingthe circuit between staging layer 110 and contact 108. Conversely, whenthe angle (alpha) is greater than 90 degrees, the magnetic moment (m) incantilever 112 points from end 132 toward end 130, creating a clockwisetorque about end 130. The clockwise torque moves end 132 downward tocomplete the circuit between staging layer 110 and contact 108. Becausethe magnetization (m) of cantilever 112 does not change unless the angle(alpha) between the long axis of cantilever 112 and the applied magneticfield 134 changes, the applied torque will remain until an externalperturbation is applied. Elastic torque of the cantilever or a stopper(such as the contact) balances the applied magnetic torque, and thusrelay 100 exhibits two stable states corresponding to the upward anddownward positions of cantilever 112 (and therefore to the open andclosed states, respectively, of relay 100).

Switching may be accomplished by any suitable technique that reversesthe direction of the cantilever's magnetic dipole moment. In anexemplary embodiment, switching may be accomplished by generating asecond magnetic field that has a component along the long axis ofcantilever 112 that is strong enough to affect the magnetization (m) ofcantilever 112. In the embodiment shown in FIG. 1, the relevantcomponent of the second magnetic field is the component of the fieldalong the X-axis. Because the strength of the second magnetic fieldalong the long axis of cantilever 112 is of primary concern, the overallmagnitude of the second magnetic field is typically significantly lessthan the magnitude of magnetic field 134 (although of course fields ofany strength could be used in various embodiments). An exemplary secondmagnetic field may be on the order of 20 Oersted, although of coursestronger or weaker fields could be used in other embodiments.

The second magnetic field may be generated through, for example, amagnet such as an electronically-controlled electromagnet.Alternatively, the second magnetic field may be generated by passing acurrent through conductor 114. As current passes through conductor 114,a magnetic field is produced in accordance with a “right-hand rule”. Forexample, a current flowing from point 126 to point 128 on conductor 114(FIG. 1B) typically generates a magnetic field “into” the center of thecoil shown, corresponding to field arrows 122 in FIG. 1A. Conversely, acurrent flowing from point 128 to point 126 in FIG. 1 generates amagnetic field flowing “out” of the center of the coil shown,corresponding to dashed field arrows 124 in FIG. 1A. The magnetic fieldmay loop around the conductor 114 in a manner shown also in FIG. 1A,imposing a horizontal (X) component of the magnetic field on thecantilever 112.

By varying the direction of the current or current pulse flowing inconductor 114, then, the direction of the second magnetic field can bealtered as desired. By altering the direction of the second magneticfield, the magnetization of cantilever 112 may be affected and relay 100may be suitably switched open or closed. When the second magnetic fieldis in the direction of field arrows 122, for example, the magnetizationof cantilever 112 will point toward end 130. This magnetization createsa clockwise torque about end 130 that places cantilever 112 in a “down”state that suitably closes relay 100. Conversely, when the secondmagnetic field is in the direction of dashed field arrows 124, themagnetization of cantilever 112 points toward end 132, and acounter-clockwise torque is produced that places cantilever 112 in an“up” state that suitably opens relay 100. Hence, the “up” or “down”state of cantilever 112 (and hence the “open” or “closed” state of relay100) may be adjusted by controlling the current flowing throughconductor 114. Further, since the magnetization of cantilever 112remains constant without external perturbation, the second magneticfield may be applied in “pulses” or otherwise intermittently as requiredto switch the relay. When the relay does not require a change of state,power to conductor 114 may be eliminated, thus creating a bi-stablelatching relay 100 without power consumption in quiescent states. Such arelay is well suited for applications in space, aeronautics, portableelectronics, and the like.

Manufacturing a Latching Relay

FIG. 2 includes a number of side views showing an exemplary techniquefor manufacturing a latching relay 100. It will be understood that theprocess disclosed herein is provided solely as an example of one of themany techniques that could be used to formulate a latching relay 100.

An exemplary fabrication process suitably begins by providing asubstrate 102, which may require an optional insulating layer. Asdiscussed above, any substrate material could be used to create alatching relay 100, so the insulating layer will not be necessary if,for example, an insulating substrate is used. In embodiments thatinclude an insulating layer, the layer may be a layer of silicon dioxide(SiO₂) or other insulating material that may be on the order of 1000angstroms in thickness. Again, the material chosen for the insulatingmaterial and the thickness of the layer may vary according to theparticular implementation.

With reference to FIG. 2A, conductor 114 is suitably formed on substrate104. Conductor 114 may be formed by any technique such as deposition(such as e-beam deposition), evaporation, electroplating or electrolessplating, or the like. In various embodiments, conductor 114 is formed ina coil pattern similar to that shown in FIG. 1. Alternatively, conductor114 is formed in a line, serpentine, circular, meander, random or otherpattern. An insulating layer 106 may be spun or otherwise applied tosubstrate 104 and conductor 114 as shown in FIG. 2B. Insulating layer106 may be applied as a layer of photoresist, silicon dioxide,Probimide-7510 material, or any other insulating material that iscapable of electrically isolating the top devices. In variousembodiments, the surface of the insulating material is planarizedthrough any technique such as chemical-mechanical planarization (CMP).

Contact pads 108 and 110 may be formed on insulating layer 106 throughany technique such as photolithography, etching, or the like (FIG. 2C).Pads 108 and 110 may be formed by depositing one or more layers ofconductive material on insulating layer 106 and then patterning the padsby wet etching, for example. In an exemplary embodiment, pads 108 and110 suitably include a first layer of chromium (to improve adhesion toinsulating layer 106) and a second layer of gold, silver, copper,aluminum, or another conducting material. Additional metal layers may beadded to the contacts by electroplating or electroless plating methodsto improve the contact reliability and lower the resistance.

With reference to FIG. 2D, the contact pads 108 and 110 may be suitablycovered with a layer of photoresist, aluminum, copper, or other materialto form sacrificial layer 202. An opening 206 in sacrificial layer 202over the cantilever base areas may be defined by photolithography,etching, or another process. Cantilever 112 may then be formed bydepositing, sputtering or otherwise placing one or more layers ofmaterial on top of sacrificial layer 202 and extending over the opening206, as shown in FIG. 2E. In an exemplary embodiment, a base layer 204of chromium or another metal may be placed on sacrificial layer 202 toimprove adhesion, and one or more conducting layers 120 may be formed aswell. Layers 204 and 120 may be formed by, for example, depositionfollowed by chemical or mechanical etching. Layer 120 may be thickenedby adding another conductor layer (such as gold, gold alloy, etc.) byelectroplating or electroless plating methods. Cantilever 112 is furtherformed by electroplating or otherwise placing a layer 118 of permalloy(such as NiFe permalloy) on top of conducting layer 120, as shown inFIG. 2F. The thickness of the permalloy layer 118 may be controlled byvarying the plating current and time of electroplating. Electroplatingat 0.02 amperes per square centimeters for a period of 60 minutes, forexample, may result in an exemplary permalloy layer thickness of about20 microns. In various embodiments, an additional permalloy layer 306(shown in FIG. 3) may be electroplated on top of cantilever 112 toincrease the responsiveness of cantilever 112 to magnetic fields.

With reference to FIG. 2G, sacrificial layer 202 may be removed by, forexample, wet or dry (i.e. oxygen plasma) releasing techniques to creategap 116 between cantilever 112 and insulating layer 106. In variousembodiments, adhesion layer 204 is removed using a suitable etching orequivalent removal technique to form relay 100 (FIG. 2H). Relay 100 maythen be diced, packaged with magnet 102 (shown in FIG. 1), or otherwiseprocessed as appropriate. It should be understood that the permanentmagnet 102 can alternatively be fabricated directly on the substrate,placed on top of the cantilever, or the coil and the cantilever can befabricated directly on a permanent magnet substrate.

Alternate Embodiments of Latching Relays

FIGS. 3 and 4 disclose alternate embodiments of latching relays 100.FIGS. 3A and 3B show side and top views, respectively, of an alternateembodiment of a latching relay that includes a hinged cantilever 112.The perspective of FIGS. 3A and 3B is rotated 90 degrees in the X-Yplane from the perspective shown in FIGS. 1A and 1B to better show thedetail of the hinged cantilever. With reference to FIGS. 3A and 3B, ahinged cantilever 112 suitably includes one or more strings 302 and 304that support a magnetically sensitive member 306 above insulating layer106. Member 306 may be relatively thick (on the order of about 50microns) compared to strings 302 and 304, which may be formed ofconductive material. As with the relays 100 discussed above inconjunction with FIG. 1, relays 100 with hinged cantilevers may beresponsive to magnetic fields such as those generated by magnet 102 andconductor 114. In various embodiments, one or both of strings 302 and304 are in electrical communication with contact pad 108 when the relayis in a “closed” state. Of course, any number of strings could be used.For example, a single string could be formulated to support the entireweight of member 306. Additionally, the strings may be located at anypoint on member 306. Although FIG. 3 shows strings 302 and 304 near thecenter of member 306, the strings could be located near the end ofmember 306 toward contact 108 to increase the torque produced by magnet102, for example.

FIG. 3C is a perspective view of an exemplary cantilever 112 suitablefor use with the embodiments shown in FIGS. 3A and 3B, as well as otherembodiments. Cantilever 112 suitably includes member 306 coupled toconducting layer 120. Holes 310 and/or 312 may be formed in conductinglayer 120 to improve flexibility of cantilever 112, and optional contactbumps 308 may be formed on the surface of conducting layer 120 to comeinto contact with contact 108. Strings 302 and 304 (not shown in FIG.3C) may be affixed or otherwise formed on cantilever 112 at any position(such as in the center of conducting layer 120 or at either end ofconducting layer 120) as appropriate. Alternatively, the strings may beformed of non-conducting materials and cantilever 112 may provide aconducting path between two separate conductors touched simultaneouslyby the cantilever in the closed state, as discussed below.

It has been observed that certain switches that include relatively widemagnetically sensitive members 306 may exhibit reduced magnetizationbecause of the relatively large ratio of the width-to-length ofcantilever 112. Moreover, the increased width may lead to increasedmagnetization along the width of cantilever 112, which may result intwisting of the cantilever and degraded contact between cantilever 112and contact 108. FIG. 3D is a perspective view of a switch that includessectionalized magnetically sensitive members 306A, 306B, 306C and 306D.To improve the magnetization along the length of cantilever 112, themagnetically sensitive member 306 may be sectionalized so that themagnetization of each member 306A-D is maximized along the length of themember instead of the width. Sectionalization may be accomplished byseparately forming (e.g. electroplating) each member 306A-D onconducting layer 120, for example, or by etching (or otherwise forming)gaps in a single electroplated layer 306. Of course any number ofmagnetically sensitive sections 306A-D could be used with variousembodiments, and the size of each section will vary from embodiment toembodiment. For example, various exemplary cantilevers 112 could befashioned with four members 306A-D of about 1000×600×25 micrometers,with eight members of about 1000×50×25 micrometers (spaced about 25micrometers apart), with fifteen members of about 1000×20×25 micrometers(spaced about 25 micrometers apart), or with any number of membershaving any dimensions. In various embodiments, interlinks of magneticmaterial, metal or any other material may be added between the members306A-D to strengthen cantilever 112. FIG. 3E is a schematic of acantilever 112 that has been formed with multiple layers. In anexemplary embodiment, cantilever 112 includes alternating layers ofmagnetic material 118 (such as permalloy) and conducting material 120,as shown in FIG. 3E, although of course other materials could be used inplace of or in addition to the materials shown. Multi-layeredcantilevers may be formed by sputtering, depositing, or otherwiseforming multiple layers as discussed, for example, in connection withFIGS. 2E and 2F above, or through any other technique. Multi-layeredcantilevers may also be sectionalized, as described above, and may beused in conjunction with any of the various embodiments of theinvention.

FIGS. 4A and 4B are side and top views, respectively, of an alternateembodiment of a latching relay 100. As shown in the Figure, variousembodiments of cantilever 112 may not directly conduct electricity fromstaging layer 110 to contact 108. In such embodiments, a conductingelement 402 may be attached to cantilever 112 to suitably provideelectrical contact between contacts 108 and 408 when relay 100 is in a“closed” state. FIGS. 4C and 4D are perspective views of alternateexemplary embodiments of cantilever 112. In such embodiments, cantilever112 may include a magnetically sensitive portion 118 separated from aconducting portion 402 by an insulating layer 410, which may be adielectric insulator, for example. Optional contact bumps 308 may alsobe formed on conducting portion 402 as shown. When cantilever 112 is ina state corresponding to the “closed” state of relay 100, current mayfollow the path shown by arrows 412 between contact pads 108 and 408, asappropriate.

FIG. 5 is a side view of an alternate exemplary embodiment of relay 100.With reference to FIG. 5, a relay 100 may include a magnet 102, asubstrate 104 and a cantilever 112 as described above (for example inconjunction with FIG. 1). In place of (or in addition to) conductor 114formed on substrate 104, however, conductor 114 may be formed on asecond substrate 504, as shown. Second substrate 504 may be any type ofsubstrate such as plastic, glass, silicon, or the like. As with theembodiments described above, conductor 114 may be coated with aninsulating layer 506, as appropriate. To create a relay 100, the variouscomponents may be formed on substrates 104 and 504, and then thesubstrates may be aligned and positioned as appropriate. The twosubstrates 104 and 504 (and the various components formed thereon) maybe separated from each other by spacers such as spacers 510 and 512 inFIG. 5, which may be formed of any material.

With continued reference to FIG. 5, contact 108 may be formed oninsulating layer 106, as described above. Alternatively, contact 508 maybe formed on second substrate 504, as shown in FIG. 5 (of coursecantilever 112 may be reformulated such that a conducting portion ofcantilever 112 comes into contact with contact 508). In otherembodiments, contacts 108 and 508 may both be provided such that relay100 is in a first state when cantilever 112 is in contact with contact108, a second state when cantilever 112 is in contact with contact 508,and/or a third state when cantilever 112 is in contact with neithercontact 108 nor contact 508. Of course the general layout of relay 100shown in FIG. 5 could be combined with any of the techniques and layoutsdescribed above to create new embodiments of relay 100.

FIGS. 6A and 6B are side and top views, respectively, of an alternateembodiment of a latching relay 100. With reference now to FIGS. 6A and6B, various embodiments of relay 100 may use electrostatic actuation toswitch the state of cantilever 112 instead of magnetic energy generatedby conductor 114. In such embodiments, one or more switching electrodes602 and 604 may be deposited or otherwise fashioned on insulating layer106. Electrodes 602 and 604 may be formed of metal or another conductingmaterial, and may be electrically coupled to leads, wires or otherconnecting devices (not shown) to create an electric potential betweeneither of the electrodes and cantilever 112.

Although FIGS. 6A and 6B show a center-hinged type cantilever 112,electrodes 602 and 604 and/or the principle of electrostatic actuationmay be included in any of the relays or switches described herein inplace of (or in addition to) the magnetic actuation produced byconductor 114. In various embodiments, electrodes 602 and 604 aresuitably positioned with respect to cantilever 112 such thatelectrostatic forces generated by the two electrodes have opposingeffects on cantilever 112. In the center-hinged embodiment shown inFIGS. 6A and 6B, for example, electrodes 602 and 604 may be positionedon either side of hinge 110 so that a voltage difference betweenelectrode 602 and cantilever 112 “pushes” cantilever 112 into an “open”state. Conversely, a voltage difference between electrode 604 andcantilever 112 may “pull” cantilever 112 into a “closed” state wherebycantilever 112 is in contact with contact 108. In such embodiments, thestate of cantilever 112 may be held by the magnetic field generated bypermanent magnet 102, and a bistable switch may result. The relay may beswitched between stable states by providing an electric potential to theappropriate electrode to attract cantilever 112 as appropriate. In anexemplary relay 100, a hinged type cantilever 112 having dimensions ofabout 1000×200×20 micrometers and a supporting torsion string 110 withdimensions of 280×20×3 micrometers may require a voltage of about 37volts, when the overlap area between the cantilever and electrode is onthe order of 200×400 square micrometers or so, to switch cantilever 112in a permanent external magnetic field of about 200 Oersted. Again,switches or relays can be formulated with any dimensions orarchitectures, and the voltage required to switch between states willsuitably vary from implementation to implementation. In particular, theelectrostatic switching technique using electrodes 602 and 604 can beincorporated into any of the relays discussed above, or any of theswitches described herein. Advantages of using electrostatic switchingover magnetic switching include reduced power consumption and ease inmanufacturing, since electrodes 602 and 604 can be very thin (e.g. onthe order of about a hundred angstroms to about 0.5 micrometers thick).Moreover, electrostatic switches may be made to be smaller than somecorresponding magnetic switches, thus reducing the overall size of theswitching device. Switching control may be provided by an control devicesuch as a microcontroller, microprocessor, application specificintegrated circuit (ASIC), logic circuit, analog or digital controlcircuit, or the like. In an exemplary embodiment a controller providescontrol signals in the form of electrical signals to electrodes 602 and604 to create voltage differences as appropriate.

It will be understood that many other embodiments of the various relayscould be formulated without departing from the scope of the invention.For example, a double-throw relay could be created by adding anadditional contact 108 that comes into contact with cantilever 112 whenthe cantilever is in its open state. Similarly, various topographies andgeometries of relay 100 could be formulated by varying the layout of thevarious components (such as pads 108 and 110 and cantilever 112).

Optical Switches

The mechanisms, principles and techniques described above in conjunctionwith electrical relays may also be used to create optical switchessuitable for use in communications or other optical systems. In variousembodiments of an optical switch, the magnetically sensitive portion ofcantilever 112 may be affixed to a mirror or other material thatreflects light. As the cantilever is switched from an “open” state to a“closed” state, the reflecting surface is exposed or hidden from anoptical signal such that the signal is reflected or absorbed asappropriate, and as described more fully below.

FIGS. 7A and 7B are side and top views, respectively, of an exemplaryoptical mirror 700 (referred to herein as a “Type I” mirror). Like theelectrical switches described above, a cantilever 112 is suitablypositioned over insulating layer 106 by a support string, hinge or otherspacer 110. Cantilever 112 may be formed of soft magnetic material 132(as discussed above), and may have a reflective coating 702 (such asaluminum or gold) deposited, sputtered or otherwise placed on themagnetic material. One or more optional stoppers 704 may be positionedon insulating layer 106, as appropriate, to receive and positioncantilever 112 as required. Stoppers 704 may be formed of any suitablematerial such as etched silicon, metal, or polyimide. In variousembodiments, support string 10 supports rotation of cantilever 112 intoan “up” state and a “down” state, as appropriate. When cantilever 112 isin an “up” state, for example, cantilever 112 may be rotatedcounter-clockwise about string 110 until end 742 of cantilever 132contacts stopper 704L. In an exemplary “down” state, cantilever 112 maybe rotated clockwise about string 110 such that the end 740 ofcantilever 112 contacts stopper 740R. When the right end of 132 touchesthe bottom stopper 704, it is in the “down”. By design, the supportingstring 110 may be placed closer to end 742 of cantilever 112 such thatcantilever 112 may be tilted to a larger angle in the “up” position thanin the “down” position. Of course, support string 110 may also be placedapproximately equidistant from the ends of cantilever 112, or such thatthe “down” position creates a larger angle, and many orientations couldbe formulated in other embodiments of the invention.

Operation of optical mirror 700 may be similar to the operation of theelectrical switches 100 discussed above. In various exemplaryembodiments, latching and switching are accomplished by inducing amagnetic torque in cantilever 112 with conductor 114 (as shown in FIG.7) or optional electrodes (as discussed above in connection with FIG.6). Cantilever 112 may be stably maintained in either the “up” or “down”state through a field generated by magnet 102, as described above.

FIGS. 8A through 8G show various views and states of a second type ofoptical mirror 800 (referred to herein as a “Type II” mirror or“reflector”). Although these devices are primarily described herein aspertaining to reflective devices used with switches or relays, theprinciples and structures described herein could be used to create anysort of actuator (reflecting or non-reflecting) that may be used in anyapplication.

With reference to FIGS. 8A and 8B, an optical mirror 800 may include acantilever 112 that includes a magnetically sensitive portion 132.Cantilever 112 may also include a reflective portion 804 with areflective coating on either or both sides. In an exemplary embodiment,reflective portion 804 has a reflective coating deposited or otherwiseplaced on face 802, as shown in FIG. 8A. One or more stoppers 704 mayalso be placed on insulating layer 106 as required to position orelevate cantilever 112 as appropriate, and a support, string or hinge110 (not shown in FIGS. 8A and 8C) may rotably fix cantilever 112 abovesubstrate 104.

In an exemplary embodiment, string 110 supports ninety degrees ofrotation between two states of cantilever 112 (plus or minus somecorrection for errors in manufacturing and the like). In the embodimentshown in FIGS. 8A and 8B, cantilever 112 is positioned into an “up”state by magnet 102 (not shown) to be approximately parallel to thesurface of substrate 104. The “up” position may be useful when it isnecessary to have a clear path for an optical beam to directly pass theType II mirror without reflection, for example. A second “down” state ofmirror 800 is shown in FIGS. 8C and 8D. Mirror 800 may be placed in the“down” state, for example, by magnet 102 (not shown) (In principle, themagnet can hold the cantilever to either of the two stable states)and/or by allowing gravity to pull the magnetically sensitive portion132 of cantilever 112 away from the “up” position. It will beappreciated that a permanent magnet 102 and a conductor 114 may not berequired for each embodiment of mirror 800, since other forces (such asforce applied by optional buckling structures on stopper 704) maymaintain cantilever 112 in the “down” position without requiringexternal forces. In many embodiments, a temporary magnetic field may beprovided while the reflective coating is applied to cantilever 112during manufacturing, and removed thereafter. In still other embodimentsof mirror 800, hinge 110 and magnetically sensitive portion 132 may beeliminated and reflective portion 804 may be rigidly fixed to substrate102 or insulating layer 104.

With reference now to FIG. 8E, an alternate embodiment of a reflector800 suitably includes a cantilever 112 and a torsion bar hinge or otheranchor 870 that may be affixed to a substrate 104. A coil or otherconductor 114 may also be provided, or an electrode capable of providingelectrostatic attraction to cantilever 112 may be provided in analternate embodiment. Cantilever 112 may be magnetically sensitive, asdescribed above, and may have one or more reflective surfaces, asdescribed above. Torsion bar hinge 870 may be implemented as one or morehinges, as described above in connection with other embodiments ofswitches or relays. In various embodiments, the torsion bar hinges maybe located at or near the end of cantilever 112 and may be fashioned tobe relatively thin and/or long with respect to cantilever 112 such thatlarge rotational deflections of cantilever 112 may take place withoutsignificant mechanical torque. Moreover, the direction of the externalmagnetic field (H_(o)) 134 applied to reflector 800 may be placed at anangle (γ) relative to a perpendicular (Z) drawn from the face ofsubstrate 104. In the exemplary embodiment shown in FIG. 8E, forexample, γ is selected to be about 45 degrees, although otherembodiments may use other angles.

The direction of magnetic field 134 suitably creates two stablepositions for cantilever 112, corresponding to an “up” state and a“down” state (cantilever 112 is shown between the two states in FIG.8E). In various embodiments, cantilever 112 may be aligned approximatelyperpendicular to substrate 104 in the “up” state, and approximatelyparallel to substrate 103 in the “down” state. A physical stopper (notshown in FIG. 8E) may be provided to maintain cantilever 112 in thedesired position for the “up” and/or “down” states.

In various embodiments, a magnetic field with a magnitude of aboutχH_(o) sin (γ+φ) Oersted or so may be provided by conductor 114 toswitch cantilever 112 between states, where “χ” is the magneticsusceptibility of cantilever 112 and “φ” is the angle between cantilever112 in the“down” state and the horizontal axis (X). A field of thismagnitude may suitably re-align the magnetization vector of cantilever112, as appropriate, similar to the switching techniques discussedabove, so that cantilever 112 switches between two stable states.Because the field generated by conductor 114 may be relatively weakcompared to the external field 134, field 134 may be designed to belarge enough to actuate device 800 but not so strong that the fieldgenerated by conductor 114 cannot reverse the magnetization vector ofcantilever 112. In an exemplary embodiment, field 134 may be designed tobe on the order of about 200 Oersted, although of course other fieldstrengths could be used. The reflector 800 described herein may exhibitapproximately 90 degrees or more of rotability, and consequently mayhave wide application beyond relays or optical switches. For example,reflectors 800 having relatively high degrees of rotability may beuseful for optical projection or switch systems.

With reference now to FIGS. 8F and 8G, a third embodiment of a reflector800 that may be used to rotate through 90 or more degrees suitablyincludes a conductor 114 placed on cantilever 112, which may be hingablyconnected to substrate 104 by a hinge 870 (shown as two torsion hinges870A and 870B in FIG. 8F). Current may be provided to conductor 114 byelectrical leads 872 (shown as leads 872A and 872B in FIG. 8F), whichmay be coupled to a source of electrical power. Alternatively,electrical contact with conductor 114 may be provided via conductivematerial (such as metal) deposited, sputtered, or otherwise placed onhinge 870. In various embodiments cantilever 112 may be made of areflective material (such as dielectric film, polycrystalline silicon,metal, non-metals or the like), since reactions to magnetic fields maybe provided by conductor 114 rather than through a magneticallysensitive material in cantilever 112. In various embodiments magnet 102provides a magnetic field H_(o), which may be provided perpendicular tosubstrate 104 or at any oblique angle, as described above in conjunctionwith FIG. 8E.

Actuation of reflector 800 may be accomplished by, for example,energizing conductor 114 with a current that produces a magnetic dipolemoment (M) that may be perpendicular to the plane of conductor 114. Themagnetic dipole moment (M) may interact with the external magnetic fieldsupplied (H_(o)) to produce a torque (T) on cantilever 112 such thatT=M×H_(o). The torque (T) may be controlled to switch cantilever 112between an “up” state and a “down” state, as described above. A moredetailed description of this principle used in a different context ispresented in Chang Liu, T. Tsao, Y-C Tai and C-M Ho, “SurfaceMicro-machined Magnetic Actuators”, MEMS '94, Oiso, Japan, pp. 57-62(1994), incorporated herein by reference.

FIGS. 9A and 9B are side and top views, respectively, of an exemplaryswitch 900 that includes two type I mirrors 700A and 700B and one typeII mirror/reflector 800. The axis of mirror 800 may be rotated 45degrees (or to any other angle) from the axes of mirrors 700A and 700Bas best seen in FIG. 9B. An optional reflective layer 902 (such as amirror) may be provided in various embodiments to reflect opticalsignals, as discussed more fully below. In various embodiments of theinvention, an optical signal (such as a pulse or beam of light) 904 isto be switched to one of two outputs 910 and 920. In the first state ofswitch 900 (shown in FIGS. 9A and 9B), cantilevers 112A and 112B ofmirrors 700A and 700B may be placed in the “up” position so that opticalsignal 904 reflects off of reflective surface 702 (FIG. 7), as shown.Reflective layer 902 suitably transmits optical signal 904 betweenmirror 700A and 700B, bypassing mirror 800 as appropriate, to outputterminal 910.

FIGS. 10A and 10B are side and top views, respectively, of opticalswitch 900 in a second state (corresponding to output terminal 920).Cantilevers 112A of mirror 700A may be placed into the “down” state sothat optical signal 904 is no longer reflected by reflective surface 702of mirror 700A, but rather reflects off of the reflective surface ofmirror 800, which may be oriented toward output terminal 920 as bestseen in FIG. 10B. Of course cantilever 112B of mirror 700B could also beplaced into the “down” position, but such a transition may not berequired since optical signal 904 does not reach mirror 700B in thestate shown in FIG. 10. Other embodiments of optical switches mayexhibit different layouts. For example, a bidirectional switch may befabricated by coating both sides of reflective portion 804 in mirror 800with reflecting material.

FIG. 11 is a top view of an exemplary 5×5 optical switch 950 that may befabricated with switches 900 as described above. With reference to FIG.11, optical signals 904A-E are received at inputs 930A-E, respectively.Each signal may be routed by switch 950 to a desired output 940A-E, asappropriate. In the exemplary switch 950 shown in the Figure, input i1is routed to output o3, input i2 is routed to output o1, input i3 isrouted to output o4, input i4 is routed to output o5, and input i5 isrouted to output o2. Of course any M×N switch fabric could beformulated, where M represents the number of inputs, N represents thenumber of outputs, and M and N are each integers. For example, 1×4switches, 4×8 switches, 8×16 switches, 2×2 switches, or any other switchfabric could be formulated by adjusting the number of switches 700 and800.

With continued reference to FIG. 11, an exemplary 5×5 optical switch mayinclude a matrix of twenty-five type II mirrors and eighty type Imirrors. The type II mirrors (shown as diagonal rectangles) may bearranged such that each input 930 has a type II mirror corresponding toeach output 940. The type I mirrors (shown as smaller rectangles) arearranged as appropriate to deflect optical signals 904 around the typeII mirrors as desired by reflecting the signals off of reflective layer902 (not shown in FIG. 11, but shown in FIG. 9A). To route signal i5 tooutput o2, for example, type I mirrors 751 and 752 may be placed intothe “up” state to deflect signal i5 around mirror 851. Type I mirrors753 and 754 may be placed into the “down” position to allow signal i5 todeflect off of type II mirror 852 toward output 940B. As describedabove, the various type I mirrors may be held in the “up” or “down”states by a magnetic field generated by a magnet 102. The variousmirrors may be switched between states by generating appropriatemagnetic pulses via a conductor 114 (FIG. 7) or electrostatic pulses viaelectrodes 602/604 (FIG. 6) to create a torque that moves theappropriate cantilever 112 to create the desired state for the desiredmirror.

The corresponding structures, materials, acts and equivalents of allelements in the claims below are intended to include any structure,material or acts for performing the functions in combination with otherclaimed elements as specifically claimed. Moreover, the steps recited inany method claims may be executed in any order. The scope of theinvention should be determined by the appended claims and their legalequivalents, rather than by the examples given above. Finally, it shouldbe emphasized that none of the elements or components described aboveare essential or critical to the practice of the invention, except asspecifically noted herein.

What is claimed is:
 1. A network for switching optical signals, saidnetwork comprising: a permanent magnet producing a first electromagneticfield; a plurality of optical inputs accepting said optical signals; aplurality of mirror elements, each mirror element comprising acantilever and an electromagnet, said cantilever having a magneticallysensitive portion and a reflective portion, said magnetically sensitiveportion having a longitudinal axis and being responsive to said firstmagnetic field to produce a magnetization vector along said longitudinalaxis, and said electromagnet being configured to switch said cantileverbetween a first state and a second state by a temporary current appliedthrough said electromagnet producing a second magnetic field such that acomponent of said second magnetic field is substantially parallel tosaid longitudinal axis to change the direction of said magnetizationvector along said longitudinal axis; and a control device controllingsaid electromagnets such that said mirror elements are switched betweensaid first and second states to allow said reflective portions of saidplurality of mirror elements to direct said optical signals between saidplurality of optical inputs and a plurality of optical outputs.
 2. Thenetwork of claim 1 wherein each of said plurality of mirror elements isformed on a substrate.
 3. The network of claim 1 further comprising aplurality of reflectors.
 4. The network of claim 3 wherein said mirrorelements are configured to switchably direct at least one of saidoptical signals around at least one of said reflectors.
 5. The networkof claim 4 wherein one of said reflectors and at least two of saidplurality of mirror elements form a switch.
 6. The network of claim 5further comprising a reflective surface configured to reflect saidoptical signals between said at least two of said plurality of mirrorelements.
 7. The network of claim 6 wherein said at least two mirrorelements direct one of said optical signals toward said reflector whensaid switch is closed, and wherein said at least two mirror elementsdirect said one of said optical signals toward said reflective surfaceand away from said reflector when said switch is open.
 8. The network ofclaim 4 wherein each of said electromagnetic signals are configured toinduce a torque in one of said cantilevers corresponding to one of saidplurality of mirror elements, such that said cantilever is switchedbetween said first state and said second state.
 9. A micro magneticoptical switch network, comprising: a substrate; at least one moveableelement supported by said substrate and having a magnetic material and areflective material, said magnetic material having a longitudinal axis;a permanent magnet producing a first magnetic field that induces amagnetization in said magnetic material, said magnetizationcharacterized by a magnetization vector along said longitudinal axis,wherein said first magnetic field is approximately perpendicular to saidlongitudinal axis; and an electromagnet producing a second magneticfield to switch said at least one movable element between two stablestates, wherein a temporary current through said electromagnet producessaid second magnetic field such that a component of said second magneticfield parallel to said longitudinal axis changes direction of saidmagnetization vector thereby causing said movable element to switchbetween said two stable states and to thereby position said reflectivematerial to switch an optical signal passing through said optical switchnetwork.
 10. The device of claim 9, wherein said electromagnet comprisesa coil.
 11. The device of claim 10, wherein said coil is formed on saidsubstrate.
 12. The device of claim 9, wherein said moveable elementcomprises a cantilever supported by a hinge on said substrate.
 13. Thedevice of claim 12, wherein said hinge supports said cantilever at abouta center position along the long axis.
 14. The device of claim 12,wherein said moveable element is located at a first side of saidsubstrate and said first magnet is located at a second side of saidsubstrate.
 15. The device of claim 9, wherein said magnetic materialcomprises a high-permeability material.
 16. The device of claim 15,wherein said high-permeability material comprises a permalloy.
 17. Amethod of operating a micro magnetic optical switch, comprising thesteps of: providing a moveable element supported by a substrate, saidmoveable element having a magnetic material and a reflective portion,said magnetic material having a longitudinal axis, producing a firstmagnetic field with a permanent magnet to thereby induce a magnetizationin said magnetic material, said magnetization characterized by amagnetization vector along said longitudinal axis; and producing asecond magnetic field with an electromagnet to switch said movableelement between two stable states, whereby a temporary current throughsaid electromagnet produces said second magnetic field such that acomponent of said second magnetic field parallel to said longitudinalaxis changes direction of said magnetization vector thereby causing saidmovable element to switch between said first and second stable statesand to thereby switch an optical signal between a first and a secondoutput.
 18. The method of claim 17 further comprising providing areflector configured to receive and reflect the optical signal when themovable element is in the first state.
 19. The method of claim 18further comprising providing a reflective surface adjacent the movableelement and the reflector.
 20. The method of claim 19 further comprisingthe step of routing the optical signal around the reflector and towardthe reflective surface by placing the movable element into a secondstate.